Objective: Previous cross-sectional studies in adolescents with early-onset schizophrenia (EOS; onset of psychotic symptoms by 18 years of age) have reported patterns of generalized neurocognitive deficits as compared to healthy comparison subjects (HCSs). Here, the authors examined the longitudinal stability of neuropsychological deficits in adolescents with EOS relative to HCS and the associations of these deficits with short-term functional outcome in patients. Method: Fifty-two subjects (26 EOS, 26 HCS) were evaluated using a comprehensive neuropsychological test battery a median of 13 months after baseline examination. The stability of scores and the relationship between baseline test performance and functional outcome in patients was explored. Results: Adolescents with EOS were impaired across neurocognitive domains at baseline and follow-up compared to HCSs; these deficits remained relatively stable over time. Follow-up social/communication, personal living, and community living skills were significantly related to attention/vigilance, working memory and verbal memory at baseline; individual cognitive domains were more strongly related to functional outcome than a global measure of intelligence. Conclusions: Neuropsychological impairment in patients with EOS appears to remain relatively stable over time regardless of changes in clinical state. In addition, this report offers preliminary support for a longitudinal relationship between neurocognitive performance in specific domains and functional outcome. (Contains 4 tables and 1 figure.)